1. Field of the Invention
The present invention relates to a washing machine that supplies metal ion added water from ion eluting means to a laundry tub (a drum or a washing tub) and performs an antibacterial treatment on the laundry being put in the laundry tub, and more particularly, to a washing machine that corrects imbalance in the laundry tub at the time of rotation for spin-drying.
2. Description of the Related Art
When laundry is washed in a washing machine, a treatment substance is frequently added to water (in particular, rinsing water). Typical examples of such a treatment substance are a fabric softener and starch. In addition to these, the demand for a finishing treatment to render laundry antibacterial has been increasing in recent years.
From the hygienic point of view, it is desirable that laundry be dried in the sun. However, in recent years, with the increase in the number of working women and with the increase in the number of nuclear families, there have been an increasing number of households where no one is at home during the daytime. In these households, there is no choice but to dry laundry indoors. Even in households where someone is at home during the daytime, laundry is dried indoors when it is raining.
When laundry is dried indoors, compared to when laundry is dried in the sun, bacteria and mold readily propagate in the laundry. This tendency is marked when laundry drying takes time such as when humidity is high like in a rainy season or when temperature is low. Depending on the propagation condition, there are cases where laundry becomes smelly.
Moreover, recently, with growing awareness of thriftiness, more and more households reuse water that is left in the bath tub after bathing, for laundry washing. However, bacteria have increased in water left in the bath tub overnight, and the bacteria adhere to laundry and further propagates to make the laundry smelly.
For this reason, there is a strong demand that an antibacterial treatment be performed on clothes to suppress the propagation of bacteria and mold, from households having no other choice but to dry laundry indoors every day and households reusing water left in the bath tub for laundry washing.
On the other hand, many clothes having undergone an antibacterial and deodorizing treatment or a microbial control treatment have recently been available. However, it is difficult that the textile goods in a household are all ones having undergone an antibacterial and deodorizing treatment. Moreover, the efficacy of the antibacterial and deodorizing treatment decreases as textile goods are washed repeatedly.
Under these circumstances, an idea was conceived of performing an antibacterial treatment on laundry every time it is washed. For example, Patent Document 1 discloses an electric washing machine provided with an ion generator that generates metal ions having sterilizing power such as silver ions or copper ions. Patent Document 2 discloses a washing machine provided with a silver ion adding unit that adds silver ions to cleaning water. In particular, in the washing machine of Patent Document 2, silver ions are added to water in a concentration of 3 to 50 ppb (part per billion) to render the laundry antibacterial.
Patent Document 1 is Japanese Unexamined Utility Model Application Publication “Utility Model Laid-Open No. H5-74487 (laid-open on Oct. 12, 1993).” Moreover, Patent Document 2 is Japanese Unexamined Patent Application Publication “Patent Application Laid-Open No. 2001-276484 (laid-open on Oct. 9, 2001).”
The washing machines of Patent Documents 1 and 2 are both so-called vertical washing machines (vertical washing) where the washing tub is disposed so that the rotation axis thereof is in the vertical direction. However, in recent years, so-called slanted washing machines (drum washing) where the drum is disposed so that the rotation axis thereof is at an angle with respect to the vertical direction have also been developed.
In vertical washing machines, since the rotation axis of the washing tub is in the vertical direction, the gravity acting on the laundry is in a direction parallel to the rotation axis. In this case, leaning does not readily occur in the washing tub, and the center of gravity of the laundry is apt to be on the rotation axis. Consequently, imbalance does not readily occur, either. Here, imbalance refers to a phenomenon in which when the laundry being put in the washing tub is not evenly spread in the washing tub, the washing tub cannot keep its balance at the time of start of rotation for spin-drying and the washing tub and the washing machine body largely shake in the subsequent spin-drying operation. Moreover, in vertical washing machines, the center of gravity of the washing tub is on the rotation axis that is in the vertical direction, and the rotation axis is situated immediately above the motor. For this reason, the load of the washing tub can be sustained by the motor portion.
On the other hand, in slanted washing machines, since the rotation axis is not in the vertical direction, the gravity acting on the laundry is not in the direction of the rotation axis. That is, when the drum is stopped, the laundry gathers in a lower part of the drum, and under that condition, the center of gravity of the laundry is not on the rotation axis. When the drum is rotated and the centrifugal force acts on the laundry, the laundry is pressed in the circumferential direction of the drum, and when the laundry is not uniformly pressed, imbalance occurs. Consequently, in slanted washing machines where the rotation axis is not in the vertical direction, the frequency of occurrence of imbalance is extremely high because of its structure.
Therefore, it is necessary to correct such imbalance, and a common method of correcting this is to pour water into the drum and agitate it to thereby slightly change the disposition of the laundry. However, only pouring water into the drum cannot make it possible to maintain the efficacy of the antibacterial treatment that is performed with time and trouble being taken, because the metal attached to the laundry in the upstream operation of the spin-drying operation is lost. This problem also arises when imbalance occurs in vertical washing machines.